- 106 -

y/.BIiS (Continu cd)

Sample

Grouping

Step

Oxide

Considered

Intercept

Regression

Coefficient

Standard Error

of Regr’r.sion

Coefficient

Calculaisd t

Values

slag ce:-3hts s t k c t h a n slag cements stronger than

1800 N x 10,;/ai2 - UEIGirr 5: 1800 N x 10V®2 - MOLE £

1 2 5 4

C S A M

1138 1700 2011 162743

Calculated F

Value

Significant Val­

ues for 999$ Prob.

Standard Error

of Estimate

-17.3 -16.7

0.7

27.1 26.6 27.0

rv .1 21.4

19.8

13.7 •’-3.4 18.5

1.32 0.73

.0.05

1.98 1.93 1.^6

3. SO 2.92 ',*Ro

3.75 3.75 3.75

14.15 1^.15

269.1 271.6 293.3

Multiple

Correlation

Coefficient

-1?.2 -21.2 -1626

-8 .1 -16.10

-1601

24.0 22.5 21.0 -1588

• & .;:r *> '>n

. .f •- 4*{i‘v

14.5 17.8 1504

19.5 1510 1501

12.2 12.0 12.9 1508

1.19 1.19 1.03

0.41 1.07

1.07

1.97 1.87 1.63 1.05

?.88 2.70 1.74 1.61

3,.75 3.75 3.75 3.75

14.15 14.15 H.15 1***15

269.3 274.7 294.7 304.9

0.47 0.49 0.44 0.46

0.47 0.51 0.45

i due to '11 condition of data

. Step could not be completed due

a regression equation docnot provide sufficient inform .tion to Tot

ulate fi alip composition

The results of the 10.RA merely confirm the findings of the pre­

vious .section: no satisfactory linear relationship exists between slag

composition and hydraulic properties.

- 108 -

�here

F = ionic field strength

Z a valency of the iou

r = ionic radius.

Thus the ionic field strength is a measure of the tendency of the ion

to co-ordinate itself with neighbouring oxygen atoms. Ionic field

(28)strengths for the oxides in question are :

F = 7r2

Si*" - 23.3

Al*5 - 12.0

<4.7

Ca4-2 - 2.04.

Thus it can be seen th t the cationic strength of network formers

iB high, that of network modifiers, low, and intermediate oxides possess

an intermediate ionic field strength. Those ions of an intermediate

nature, can, to a limited extent, replace Si"* ions in the tetrahedral

arrangement of the (SiO,,)-** "building block." «hile modifying oxides can

only be situated between the (SiO,,)-'* tetrshedra. Al’3 ions, for ex­

ample, because of their intermediate ior.ic field strength con assume

either a modifying or foming role in th. silicate structure. When re­

placing Si*** in the basic silica tetrahedra, Al*5 assumes four-fold co­

ordination provided other cations ore present to provide electrical

neutrality, while as « modifier it has six-fold coordination.

A. other oxides are mixed with the main network former, silica,

. certain amount of Juggling occur, with regard to th, spatial ..range-

'/he^eas r*ire has each silicon ion

ment of the anions and cations, . 2

__ the addition of a email eaount of a net-

bonded with four oxyt.en '•* *

« breakage i" t’ne dual bonding of the

work modifier, say CaO, causes a breakage

• two silicon ions,

bridging oxygen ions to two sj.

unbonded oxygensingly bonded or

ron-bridging

doubly bonded

or bridging

- 110

between composition nd liquiduG temperature do not exist over extended

compositional areas except at the corners wher the composition consists

of essentially one oxide, "veil in particular phase fields, varying

slopes ore present preluding straight-line functions from existing.

If the comparatively simple mechanism of liquifaction (hence liq­

uidus temperature) fails to exhibit linear functions with composition,

there should bp little reason to hope for widespread correlation be­

tween hydraulic activity (a rather complex mechanism depending upon

several external factors such as fineness, temperature, amount of ac­

tivation, etc.) and composition. Thus although a few conclusions can

be made concerning the statistical analysis, these confirm the leason-

ing that the hydration of clogs is much too complex a reaction to be

governed by relatively simple relationships.

1+.3 Kelationnhir- 0tv-'?r mhnn Compositional

The previous sections point out that only limited relationships

„ i . t between exposition and stren5th. It was therefor, decided to

assess the strength c*hilitod b, a slaB on soco crit.ri. other then ooc-

position, -nd to deter,!.. if . =enninef.l rolstionship could be derived.

The criteria chosen » the total co.hinod voter of hydration.

Th. non-evaporable water is a »«a=ur« of the deeree of hydration

i„ s cement paste. Thus if two id.nticl c e n t p>stes are allowed to

hydrate for a period of ti.e, the one contain^ the noot nnn-

CVBporoble water would bo the -ore c»plete,y reacted hence the stronger.

1». 3 .1 Sample r.election

, L 51 that silica and lime are generally theIt was shown (Scction «».2) that

. . i n a slag cement in regard to stren ;th.

most important constituents in a slag

for the measurement of the non-evaporable water were

Thus samples chosen fo

. ti n cirht samples of the dried 28-day test based or this consideration. - W

c 12 C-13, C-1J*, and c“15 based on acylinders were chosen. These were

- 111 -

conntant silica m d alumina l.,vel, C-2 and 0-2*1 based on a const: nt

C/M ratio and alumina level, and B-13 anC D-13 based on constar.t.

r itio r xlicj 1 >vel. I'heae sanples form a rough three-dinensional

cross with sample C-13 as the centre pcint. Such an arrangement of

samples includes compressive strengths between 8:0 and 2270 N x 1 o V m 2 .

If a relationship between the combined water and strength exists,

the stronger slag cements should have a greater amount of combined

water. The non-evaporable water contained in a dried cement paste can

bo attributed to two sources: (1) combined water of hydration and (2)

water fixed in Ca(0H)- durir.g hydration. Particularly in the synthetic

slags tnder investigation where 15 per cent CaCOH)^ was intentionally

added as activator the amount of water contained in unreacted acti­

vator must be determined and applied as a correction to the total com­

bined water in the sample.

k. 3.2 The mo-gravimetric Analysis

_3

Ground samples of the over»-dried cement weighing 1 x 10 kg were

placeu in a Stanton thcrmo-gravimetric analyzer (TGA) and heeted from

room temperature (nominally to at a rate of per ain-

ute under rtmcspheric conditions. A typical first derivative curve

( A W / A T ) resulting from this test is shown as Figure 20. The peak

that occurs at about 35 minutes (approximately is attributed to

the loss of combined water of hydration. The peak oceurlng subsequently

at 70 - 100 minutes (^50 - was taken as the loss of weight from

the dissociation of height loss from the dissociation of CaCOj

(if any) was included in the weight loss of calcium hydroxide.

• u nf each sample, the weight loss attributed

The total weight loss ol eacn oaayj. ,

. r„(Cv) and, by difference, the weight of com-

to the dissociation of CalO.Ug ana’ J

bined water . « shown in Table XI. The th.or.tic.1 ~ou»« of Ca<0H>2

i„ each ample wan ecpotcd and «1~ **“• « •

- 113 -

k lU & f i .1

^•3«5 X-ray Diffraction Analysis

In addition to the TUA work, the sanples were subjected to X-ray

’iffraction analysis using the Fhilipa goniometer scanner. It waa hoped

th -t the presence of unrenctod calcium hydroxide or hydraticn products

could be detected. Only the filler sand (pure SiO^) could be identified,

and all peaks recorded were associated with the Si02-

h.J.k Discussion of Results of Non-ev.- porable Vfater Tests

Only 25 per cent of the original solid mort'-ir constituents wero

reactive, the remainder being inert filler sand. In oi'der to determine

the percentage combined water of each sample, the sample weight loss

must be applied to only the reactive portion. Thus a combined water

loss of 20 x 10”' kg for the entire sample yields eight per cent com­

bined water for the ~.re slag. These computed values of per cent com­

bined water are shown in Table XI.

During the hydration process CatOH)^ is liberated by the reaction,

the amount of which cannot be determined. Nor can the amount of CaCOH^

re-reacted be determined ence the computed amount of CaiOHjg remaining

in the sample after hydration includes the amount provided by the hy­

dration reaction as well as that added as an activator.

The total weight losses of the simples were so n u l l than

five per cent) that the accuracy of the TGA work is questionable. There

appears to he no definite relationship between th. combined water or the

amount of unrencted hydrovid, and strength. Even though the

two strongest slags contained the highest per cent of combined water,

the weakest sln8 contained a greater amount th* other, stronger slags.

than that exhibited between strength

This trend is no more significant

and composition.

Increased production of iron, steel, and ferro-alloys hats produced

large quantifies of blag from tr.ese operations. Tlvs composition of

these slags f-lls generally into the quaternary system

CaO which, depending upon other considerations, may ratskc them suitable

for the cement industry. Formerly the composition of slag to be uaed

for cement was rigidly controlled so th it the effects of line and nag-

nesia unsoundness (the cause of which v/as net clear) would not be ex­

perienced. Kecent work h:\s shown the causes of unsoundness and methods

to eliminate it have been proposed has expanded

the composition range of slags suitable for use as cement.

In nddition to composition, other characteristics may affect a

sing's behaviour as a cement. These include the crystallizing poten­

tial, presence of foreign material not belonging to the quaternary cys-

tem, fineness, amount of activaMon, and other factors. Although sr je

investigations h*ve been made into high-alumin* and high-magnesia slags

fo use as cement, the entire range of slags available for use as ce­

ment has not been investigated. this in nind, 101 slag compositions

were selected for the purpose of investigating their hydraulic proper­

ties. The compositions of these slags are shown in Table II.

Of interest was the quenching behaviour of the slag samples. If

they could not be successfully quenched to form a glass, their

cation .. . cement would be hindered. Th. Uquidu. temperature of oil

th. samples was determined s, that .11 could be quench.d from the same

temperature above the liquidus temperature. The dc„ree of order that

exists in . liquid dependent upon th ■ temperature of th.

above itr li,uidus temperature. Th, liquidus temperature. as determined

are given in Table IV.

Author Coale R D Name of thesis Cementitious properties of Metallurgical slags 1971

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